A temporary solution to the problem is in the “Region and Language”. If you have a comma as separator, PowierBI building a script PythonScriptWrapper.PY and takes this setting to enter floating numbers to it and that is wrong. By default, I use Polish regional settings and I faced the same problem. After changing "Decimal symbol" to the dot, I was able to plot data with a Python script. Keep in mind that you have to change the decimal symbol's setting in "Customize Format" before launching PowerBI.